Ultra high track density adaptive head core track pitch control

ABSTRACT

Apparatuses and methods for adjusting the track pitches of the tracks on a data storage tape. In one variation, the method comprises adjusting the observed pitch between the tracks by applying variable amounts of pressure on the surface of the tape. In another variation, the pressure is applied to a localized region on the tape. The pressure can be modulated to induces a change in the physical characteristic of the tape in and around the area where pressure is applied. In another aspect, an apparatus is configured with a magnetic read-head for detecting written tracks on a magnetic tape, and an actuator is provided to apply pressure on the tape to control the track pitch of the written tracks.

FIELD OF THE INVENTION

The invention is related generally to the field of data storage systems.More particularly, the present invention is related to methods andapparatuses for controlling track pitch while writing and/or readingfrom a data storage tape.

BACKGROUND

Magnetic tape servo tracking systems' accuracies continue to improveover time, where currently, the traditional servo error, PES (PositionError Signal), is no longer the most significant tracking error. Manytape servo and tracking technologies are able to demonstrate performancecapability in the sub one micron for PES errors.

In examining the contribution of position errors to the total off-trackbudget, it is evident that core pitch and track pitch mismatch fastbecoming the dominant limitation. Unfortunately, the pitch relatederrors are embedded into the multi-channel flexible tape's geometricallimitations, and it is well understood that traditional servo controlhave difficulties in correcting pitch related errors as caused by theread-head or media. For example, typical off-track component caused bypitch error is in the range of 1-2 microns, and pitch error is by farthe largest component of off-track error in the next generation tapedrives. While this error may be insignificant in a tape drive within anerror budget in the range of 8-10 microns, the same error would beunacceptable for next generation products with much higher trackdensity.

It is also important to note that advances in tape guide andimprovements in servo technology as applied to current tape systems arefast approaching the point of diminishing return. For example, in aguiding and servo system that could reduce the position error by half,the benefit to the system is a little more than a fraction of a micron(e.g., 0.1-0.2), as only one core could benefit. However, the “mismatch”between the tape tracks and head cores is at least one order ofmagnitude higher. Therefore, in the next generation systems the trackpitch error is a major limiting factor towards increasing trackdensities.

In a system with dedicated servo technologies that use “surrogate servosensors”, such as optical or magnetic heads, the accuracy is furtherlimited by the system's inability to observe this mismatch as seen bythe various data transducers or head cores. Therefore, only the staticportion of the error could be corrected. The system would not be able toaccommodate the dynamic changes in track pitches along the length of thetape.

In addition, it is well known in the tape industry that mismatch betweenthe read-head (e.g., head cores, etc.) and the multiple data trackswritten on a given tape can be a significant contributing cause ofoff-track error. Typically mismatch can be caused by two factors. First,when data is interchanged between two drives, the respective headsintroduce core pitch mismatch between the two written data sets. Withthe advances of thin film head technology, mismatch has been reduced incomparison with traditional ferrite heads designs. However, at ultrahigh track densities, such as 10K TPI (Tracks Per Inch) and beyond, thismismatch becomes very significant. The second mismatch errorcontributor, which can occur even at lower TPI, is the differences inthe expansion characteristic between the head and tape media due toenvironmental changes. The media can expand significantly due to thermaland/or hydroscopic variations.

Therefore, there is a need for methods and apparatuses that permit amagnetic tape drive to compensate for the dynamic changes in trackpitches on the magnetic data storage tapes. In particular, the abilityto adaptively modify track pitches of the magnetic tape to match thetransducers on a magnetic read-head can enhance the performance of tapedrives that utilize magnetic tapes with high track density.

SUMMARY OF THE INVENTION

Disclosed herein are apparatuses and methods for adjusting the trackpitches of the tracks on a tape media. In one example, the methodcomprises adjusting the observed pitch between the tracks by applyingvariable pressure gradient on the surface of the magnetic tape. In onevariation, the pressure is applied to a localized area on the magnetictape. The pressure is modulated to induce a change in the physicalcharacteristic of the tape in and around the area where the pressure isapplied. For example, as a pressure is applied onto the tape by anactuator stretching a local surface region, the distance across thewidth of the tape expands and “pushes apart” the written tracks in thisregion. As the pressure being applied by the actuator is decreased, thelocal surface region on the tape relaxes and “pulls together” thewritten tracks in this region.

This method can be implemented with active control and/or adaptiveresponse, such that track pitches for the tracks to be read by themagnetic read-head can be expanded or contracted in order to match thetracks to their corresponding magnetic transducers (e.g.,magneto-resistive sensors, etc.) on the read-head. “Match” as usedherein means adjusting the tracks so that the positions of the trackscorrespond to the positions of the magnetic transducers, such that dataon each of the tracks can be read by a corresponding magnetic transduceron the read-head.

By continuously monitoring the track pitch on the tape being read, themagnetic tape drive can be adaptively (e.g., through feed-back control)stretched or relaxed in the tape media (within an acceptable operatinglimits) in a localized region being read by the magnetic read-head toimprove the alignment between the tracks on the magnetic tape withtransducers on the magnetic read-head. In one variation, an algorithm(e.g., interpolation, fuzzy logic, neural network, etc.) can beimplemented to calculate a best fit between the tracks on the magnetictape with their corresponding magnetic transducers on the read-head.

In another variation, a controller is implemented to monitor the changesin track pitches along the length of the tape as the data on the tape isbeing read. As the track pitches on the tape changes, an actuator isutilized to expand or contract the tape in a localized region, and as aconsequence, inducing the tracks in this localized region to either moveaway or move towards each other in such a way as to maintaincorrespondence between the tape tracks and the magnetic transducers onthe read-head. For example, the controller can be configured tocontinuously monitor the track pitches and adjust the track pitches suchthat an approximate fit between the tracks and their correspondingmagnetic transducers on the read-head is maintained as the data isdownloaded from the tape.

In one application, the track pitch control function can be applied tocorrect expansion errors as measured by a pre-written servo tracks orFAF/CAF (Fast Access Format/Course Alignment Field) type calibrations.In another variation, the track pitch control function can be applied ina system without pre-written servo tracking technologies, such as anauto tape servo. The auto-servo system, such as one disclosed in U.S.patent application Ser. No. 11/084,412 entitled AUTO-SERVO TAPE SYSTEMAND ASSOCIATED RECORDING HEAD, is capable of measuring the as writtenpitch error from the actual data tracks and can have more actualinformation than the surrogate type servo tracking as measured byconstant pitch dedicated servo tracks, which are preset during thefactory servo writing process. In yet another variation, embedded servotechnology, such as the write and/or read servo, is combined with thetrack pitch control function, to allow the tape drive to detect andcorrect off-track error, as well as the mismatch between thetrack-pitches on the tape and the spacing separating the magnetictransducers on the magnetic read-head (e.g., head core pitch).

These and other embodiments, features, and advantages of the presentinvention will become more apparent to those skilled in the art whentaken with reference to the following more detailed description of theinvention in conjunction with the accompanying drawings that are firstbriefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one example where off-track error occurs due tomismatch between magnetic transducers on the read-head and the writtentracks on the magnetic data storage tape.

FIG. 2 illustrates another scenario where various error/noise occursover time due to drifts/changes in written track along the length of thetape. This misalignment of tracks on the magnetic tape may be due totransfer of the tape media between different tape drives.

FIG. 3 illustrates one example where a transducer is implemented in atape drive to correct variation in track pitches. As shown, the actuatorcan be utilized to apply a downward force onto the tape surface, whichleads to an increase in localized tape tension to increase the trackpitch of the written tracks on the tape.

FIG. 4A is a perspective view illustrating another variation inimplementing an actuator to deliver a localized pressure on the magnetictape. In this variation, the lateral dimension, W₁, of the portion ofthe actuator that contacts the tape is less than the width of the tape,W₂.

FIG. 4B is a top view illustrating one example where an actuator isutilized to maintain alignments between magnetic transducers on theread-head and the written tracks having varying regions of trackpitches.

FIG. 5 illustrates another combination, where two actuators areimplemented to apply pressure, both in front and behind the magneticread-head.

FIG. 6 illustrates yet another variation wherein a roller is implementedon the actuator to apply pressure onto the surface of the tape.

FIG. 7A illustrates another example of utilizing an actuator to modifythe track pitch on a set of given tracks. In FIG. 7A, the actuator isshown disengaged from the surface of the tape, and the two outer trackson the tape are miss-aligned with the two outer transducers on theread-head.

FIG. 7B illustrates the apparatus shown in FIG. 7A with the actuatordepressed into the surface of the tape, causing the tracks on the tapeto expand outward away from each other within a localized region of thetape, resulting in the alignment of the tracks with the transducers onthe read-head.

FIG. 8 is a flow chart illustrating one example of a method forcontrolling track pitch.

FIG. 9 illustrates another example of a read-head/actuator combination.In this example, the magnetic read-head is positioned over the top sideof the tape, while the actuator is positioned to apply pressure to theunderside of the tape.

FIG. 10 illustrates yet another example of read-head/actuatorcombination, where two actuators are positioned on each side of themagnetic read-head to apply pressure to the surface of the magnetictape.

FIG. 11 illustrates another design variation, where a singledisplacement mechanism is configured to apply pressure at locationsimmediately before, and immediately after, the magnetic read-head. Inthis particular example, the contacting elements, which extend beyondthe width of the tape, and are coupled to a displacement device.

FIG. 12 illustrates one variation where the read-head itself isdisplaced into the surface of the tape directly to induce a change inthe track pitch of the written track on the magnetic tape.

FIG. 13 illustrates one configuration where the moveable magneticread-head is implemented along with two fixed-position counter supports,which are placed on the other side of the tape. In this example, boththe magnetic read-head and the two counter supports are configured withlateral dimensions less than the width of the tape.

FIG. 14 illustrates another variation, where both the magnetic read-headand its corresponding counter supports are movable.

FIG. 15 shows another variation where the two actuators are provided onthe same side of the tape, next to the read-head.

FIG. 16 shows yet another variation where the two pressure deliveryelements are coupled to the magnetic read-head.

FIG. 17 shows an example where two actuators are positioned next to oneanother to deliver pressure onto the tape on one side of the magneticread-head.

FIG. 18 illustrates another approach where varying amounts of pressureare being applied across the contacting surface of the actuator. Asshown in FIG. 18, a single actuator is configured with a plurality ofelements to deliver varying amounts of pressure across the distal tip ofthe actuator.

FIG. 19 illustrates one design variation where a buffering mechanism ispositioned at the distal end of the actuator elements to provide asmooth force/pressure profile across the effected region on the tape.

FIG. 20 illustrates another variation of an actuator for deliveringvarying amounts of force/pressure within a section along the width ofthe tape.

FIG. 21 illustrates yet another example of an apparatus for controllingtrack pitch locally on a tape being read by a tape drive. In thisexample, the overall tape tension is held constant, while an actuator isutilized to modulate tape tension in a localized region on the tape.

FIG. 22 illustrates one design variation where the actuator comprises arollable drum. By controlling the orientation of the rollable drum, thecontroller in the apparatus is able to control the tape tension in alocalized region surround the area of the tape being read by themagnetic read-head, and thereby modify the track pitch locally.

FIG. 23 is a perspective view showing one variation of a magneticread-head having a pair of data islands, mini-outriggers and primaryoutriggers. The contour and surface characteristics of the read-headpromotes the tape to maintain contact with the read-head when the tapeis passed under the read-head at high speed.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description should be read with reference to thedrawings, in which identical reference numbers refer to like elementsthroughout the different figures. The drawings, which are notnecessarily to scale, depict selective embodiments and are not intendedto limit the scope of the invention. The detailed descriptionillustrates by way of example, not by way of limitation, the principlesof the invention. This description will clearly enable one skilled inthe art to make and use the invention, and describes severalembodiments, adaptations, variations, alternatives and uses of theinvention, including what is presently believed to be the best mode ofcarrying out the invention.

Magnetic tape drive is used herein as an example application of thetrack pitch control function, in order to illustrate the various aspectsof the invention disclosed herein. In light of the disclosure herein,one of ordinary skill in the art would appreciate that the methods andapparatuses disclosed herein can be implemented in various other datastorage tapes, including optical tapes, to adjust track pitch of thewritten tracks on the tape media to improve the performance of the tapedrive.

It must also be noted that, as used in this specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, the term “a read-head” is intended to mean a single read-heador a combination of read-heads, “an electrical signal” is intended tomean one or more electrical signals, or a modulation thereof.Furthermore, “longitudinal dimension” as used herein means the dimensionon the tap along the length of the tape, and “lateral dimension” as usedherein means the dimension along the width of the tape. In addition,“track pitch” as used herein means the distance between two adjacenttracks on a tape surface. It corresponds to the tracks per inch (TPI) orthe density of tracks on a data storage tape. Moreover, magneticread-read-head means a magnetic head comprises a plurality of magnetictransducers for sensing magnetic variations on a magnetic tape. Amagnetic read-head may be configured with both read and writecapability. In one variation, the magnetic read-head comprises amagneto-resistive cluster head assembly having a plurality ofmagneto-resistive transducers capable of simultaneously reading datafrom sixteen separate tracks on a magnetic tape.

In one variation, the apparatus is operable to dynamically modify theregion of the tape that interfaces with the read-head (e.g., head core)in an adaptive manner. For example, the track-pitch on the tape can beadjusted according to a signal representing the track pitch error (e.g.,core pitch error) between the magnetic transducers on the read-head andthe written track pitch on the tape. Typical thin tape media that areutilized for data recording are flexible and can expand and contractwithin its elastic limits. Thus, an actuator (e.g., roller, drum,displacement mechanism, pressure/force application mechanism, etc.) canbe utilized to deliver a localized pressure directly onto the surface ofthe tap to induce expansion of the tape in a limited area on the tape.The pitch control function utilizes an actuator to induce reversiblephysical changes to the tape by applying a pressure/force in a verticaldirection, such that the tracks on the tape are “pushed away from eachother” or “pulled together towards each other” to match the magnetictransducers' distribution pattern on the read-head (e.g., the head corepitch). This technique may be particularly useful in tape driveutilizing thin tapes with high track density. The pitch control functionmay allow the system to make micro-adjustments with the track-pitch in acontrolled manner.

FIG. 1 illustrates a current method used in DLT/SDLT tape drive to alignone set of magnetic transducers 2 on a read-head 4 to a set of writtendata tracks 6 on a magnetic tape 8. In the example shown, the datatracks on the tape are written with a magnetic transducers having atighter distribution pattern than the transducers 2 on the read-head 4.Thus, when best fit average is employed during the calibration orFAF/CAF, off-track error 10 can be observed. In this configuration, inorder to accommodate the off-track error, the error budget requires thetracks to be written wider than otherwise needed to allow read-heads tofit into tracks written by another drive.

FIG. 2 illustrates another scenario where various error/noise 12 occurover time as the tape media interchanges between drives, or read/writtenare performed at different operating temperature and/or humidity. As thetape media 14 is operated under different temperature and/or humidity,the tape media will expand or contract, resulting in changes intrack-pitches of the written tracks along the length of the tape.Without the capability to adjust the track-pitch, one would need toensure that the written tracks would be wide enough to accommodate allthese errors, even if the system is able to achieve perfect servotracking.

One approach to account for these track-pitch variations is to utilizethe pitch control function to modify the position of the tracks on thetape to fit the transducer pattern on the read-head. In one example, asshown in FIG. 3, the apparatus 22 comprises a magnetic read-headincluding a plurality of magnetic transducers for reading informationfrom a plurality of tracks on the magnetic tape. The track 24 mayinclude both data tracks and servo tracks. In one variation, customerdata are written in the data tracks. Customer data comprises informationwritten onto the tape by a customer or other user post manufacturing ofthe tape. For example, customer data may include financial and/oraccounting data generated by a company during normal course of business.The company (i.e., customer) then downloads these data onto a formattedtape media having servo tracks pre-written on them.

An actuator 26 is positioned next to the magnetic read-head 4. Theactuator is capable of applying pressure on a top surface 28 of themagnetic tape 8. In this particular variation, the actuator isconfigured to apply pressure across the width 30 of the tape. Anelectronic controller 32 is connected to both the actuator and themagnetic read-head 4. The controller receives information regardingtrack pitch (e.g., track pitch error signal, etc.) and/or track positioninformation from the magnetic read-head, then controls the actuator 26to apply a pressure onto the magnetic tape 8 to change the track pitch.The controller receives a feedback from the magnetic read-head 4regarding the changes in track pitch due to the pressure, and adjuststhe amount of pressure being applied by the actuator 26. This feedbackloop continues until the track pitch is adjusted to match the magnetictransducers distribution pattern on the magnetic read-head 4, such thatdata/information in the data and/or servo track on the magnetic tape canbe read by the magnetic transducers.

In one variation, the magnetic read-head includes eight magnetictransducers for simultaneously reading data from eight different trackson the tape. The tape drive apparatus first utilizes a servo track toalign the eight tracks on the tape with the magnetic read-head.Technology for utilizing a servo track to align tracks on the magnetictape with the read-head is well known to one of ordinary skill in theart. Optical alignment technology, which is also well known to one ofordinary skill in the art, can also be implemented to provide generalalignment (e.g., control lateral movement of the tape to center thetape) of the magnetic tape with the read-head.

Once a rough alignment is achieved, then the controller 32 utilizes theactuator 26 to adjust the track pitches on the tape 8, such that thetrack pitches approximate the spacing between the transducers on theread-head 4. In one application, the controller 32 continuously monitortrack pitch and/or track position information receive from the magneticread-head, and continuously adjust the track pitch of the tape, bymodulating compression applied by the actuator, to account forvariations in track pitch along the length of the tape. Thus, ensuringthe tracks continue to correspond to the transducers on the magneticread-head. In one variation, alignment utilizing the servo track, andalignment utilizing the actuator, are performed in parallel. In anothervariation, the feedback controller utilizes a computer algorithm (e.g.,fuzzy logic, neural network, digital filter, numerical modeling,adaptive learning, etc.) to determine a track pitch that best fit thetransducer pattern on the magnetic read-head.

FIG. 3 shows one example where the first section 34 of the tracks 24 haswider pitches than the second section 36 of the tracks 24. In order forthe read-head 4 to continue to read data from the second section 36 ofthe track 24 once the tape 8 has been advanced forward, the trackpitches in the second section 36 would need to be expanded to match thetransducers on the magnetic read-head 4. The actuator 26 can be advanceddownward to increase the pressure on the tape 8, and thereby increasingthe tension in a local region surrounding the area where the actuator 26contacts the tape 8. As the tape tension is increased in the localregion, the distances between the tracks will increase in this localregion.

Referring to FIG. 4A, another variation of implementing an actuator 26to deliver a localized pressure on a magnetic tape 8 is illustrated. Inthis variation, the lateral dimension, W₁, of the actuator 26 thatcontacts the tape 8 is less the width of the tape, W₂. As the actuatoris displaced towards the surface 42 of the tape 8, tape tension in alocalized area adjacent to the actuator contact area will be increased.By changing the tape tension locally, one can adjust the track pitcheslocally. As one of ordinary skill in the art would appreciate, two ormore channels may be provided on a magnetic tape, and each channel caninclude a plurality of tracks (e.g., 8 tracks, 16 tracks, 32 tracks,etc.). By increasing tape tension locally, the user can selectively,modify track pitch for a specific channel. In another variation, anactuator 26 can be configured to modify track pitch for two or morechannels at the same time.

Localization of tension variations induced by the actuator may minimizetear and wear to the tape in comparison to a system that stretches thecomplete tape. In particular, damages to the edges of the tape may beavoided since the actuator does not come into direct contact with theedges of the tape. Furthermore, applying an actuator to a localized areamay allow the system to deliver fine tension adjustments on the tape,and thus allowing the system to fine tune the track pitches by makingvery small tension adjustments. In addition, since the pressure isdelivered locally, a small amount of pressure may be enough to inducesubstantial change in the track pitch in the immediate area surroundingthe pressure application location. In comparison, a system that appliespressure or tension to the length of the tape may require asubstantially larger amount of pressure to induce the same amount oftrack changes in comparison to system configured to modulate tension ofthe tape locally. Therefore, the system that stretches the complete tapemay decrease the operating life expectancy of the tape media. Moreover,new generation of tape media with ultra thin configuration may besusceptible to damage or even complete failure when exposed to highlevels of tension.

FIG. 4A illustrates one example where the track comprises three sectionswith varying track pitches in one of the channels on the tape. The trackpitches contract from section “a” to section “b”, and then expand fromsection “b” to section “c”. These variations may be due totemperature/humidity change or other factors that affect the tapeproperty during the data recording session. In order for the read-headto properly trace the various tracks from section “a” through section“c”, the controller monitors the track pitch error information, which isbased on information read by the magnetic transducers in the read-head,and corrects the track pitches seen by the read-head by modifying apressure on the tape to expand or contract the distances between thetracks.

FIG. 4B illustrates one example where a servo track is utilized to alignthe channel 52 with the read-head 4. The actuator 26 maintains apressure on the tape 8 to maintain the track pitches to match thetransducers' pattern 54 on the read-head 4. As the tape 8 is advanced tothe point where the section 56 with smaller track pitches is scanned bythe read-head, the controller determines a change in track pitch thathas occurred based on information provided by the read-head and modifythe pressure applied by the actuator in order to compensate for thelarger track pitches and maintain the alignment between the tracks andthe magnetic transducers.

The actuator may be placed in front or behind the magnetic read-head. Inone variation, the actuator 26 is placed in front of the magneticread-head 4 in relation to the direction of the tape advancement, asshown in FIG. 4B. In another variation, the actuator is placed behindthe read-head. In yet another variation, two actuators 26, 27 areimplemented to apply pressure both in front and behind the magneticread-head 4, as shown in FIG. 5. The two actuators 26, 27 may beconfigured to apply pressure simultaneously or they may be controlledindependently. In configuration with either signal or multipleactuators, a lever (e.g., a L-trigger, etc.) may be further incorporatedto assist with maintaining contact between the tape and the read-head.

Furthermore, one of ordinary skill in the art having the benefit of thisdisclosure would appreciate that the actuator may be configured withvarious interfaces to engage the tape surface. In one variation, aroller 62 is implemented on the actuator 26 to apply pressure on thetape 8, as shown in FIG. 6. In another variation, the distal end of theactuator comprises a blunt pin being displaced into and out of the tapesurface. In another variation, an independent motor (e.g., piezo driver,step motor, other displacement mechanisms, etc.) is coupled to a pin,rod or other interface structures to apply pressure to an area on thesurface of the tape. In yet another variation, a balloon or a diaphragmis inflated to apply pressure to the surface of the tape. By adjustingthe amount of fluid in the balloon or the diaphragm one can control thesize of the balloon or diaphragm to modulate the pressure imposed on thesurface of the tape, and thereby control the track pitch.

FIGS. 7A and 7B illustrate another example of utilizing an actuator tomodify the track pitch for a group of written tracks on the tape. FIG.7A shows the actuator 26 disengaged from the surface 28 of the tape 8.The track pitches on these tracks 66, 68, 70 are narrower than thedistribution of the magnetic transducers 72, 74, 76 on the read-head 4.Thus, the two outer tracks 66, 70 are misaligned with the transducers72, 76. The tracks 66, 68, 70 may have been written onto the tape with amagnetic write-head having traducers that are more closely distributedfrom each other in comparison from the transducer patterns on theread-head 4. FIG. 7B shows the actuator 26 depressed into the surface 28of the tape 8 causing the tracks 66, 68, 70 on the tape to move awayfrom each other within a localized region 78 of the tape. As the trackpitch is increased, the tracks 66, 68, 70 become aligned with thetransducers 72, 74, 76 on the magnetic read-head 4.

Another aspect of the invention comprises methods for transducing datafrom a magnetic tape while controlling track pitch to match thetransducer pattern on the magnetic read-head. In one variation, themethod comprises utilizing a magnetic read-head including a plurality oftransducers to simultaneously read data from a plurality of tracks on amagnetic tape, while adjusting the track pitches of tracks to improvealignment between the tracks on the magnetic tape with the transducerson the magnetic read-head. The track pitch can be adjusted by expandingor contracting the width of the tape to match each of the tracks to acorresponding transducer on the magnetic read-head. In one variation,the tracks are adjusted by varying the tape tension in a localized areaof the tape. The localized area may be limited to an area on the surfaceof the tape where the lateral dimension is less than the width of thetape.

For example, an actuator can be used to apply pressure/force can beapplied onto a localized area on the tape. By decreasing or increasingthe pressure applied on the surface of the tape, the track pitch in theregion immediately surrounding the localized area can be modified. Inone variation, the pressure/force is applied on an area having a width(i.e., lateral dimension) that is less than 50% the width of the tape.In another variation, pressure imposed on the surface of the tape isapplied on an area with a width that is less than 25% the width of thetape. In yet another variation, the pressure is imposed on the tape tocause changes in the track pitch in an area having a width of 0.5 inchesor less. The actuator can be implemented to vary the track pitches of aplurality of tracks in order to determine a match between the tracks andthe transducers in the read-head. For example, the actuator can continueto increase the pressure on the tape to minimize track error until anover correction is detected. The controller then releases part of thepressure imposed on the tape and bring the track pitch back to a bestmatch point. By limiting the pressure to a localized area, the apparatuscan expand (e.g., stretch) one area on the tape, while keeping thetension in the rest of the area surrounding the expanded area at aconstant level. In one variation, the tape drive comprises moveableread-head and the read-head is displaced to apply pressure directly onthe tape.

FIG. 8 illustrates yet another example of a method for controlling trackpitch 82. In this example, a magnetic tape media is placed into the tapedrive by the operator. The magnetic read-head in the tape drive detectsat least one servo tracks in the tape drive 84, and then adjusts theposition of the tape laterally to align the tape to the magneticread-head 86. The magnetic read-head detects one or more track pitchesof a plurality of tracks on the magnetic tape 88. This may be done bydetecting the position of two or more tracks and then calculate thedistance between the tracks. In one variation, the method comprisesmonitoring the position of the outer two tracks in the channel. Inanother variation, track pitch is determined based on the distancebetween two data tracks. In yet another variation, the track pitch isdetermined base on the distance between a data track and a servo track.In one configuration, the track information detected by the magneticread-head is provided to an electronic circuit that calculates a trackpitch error, which can include information regarding mismatch betweenthe tracks and the magnetic transducers in the read-head. The trackpitch error is provided to a control circuit, which utilizes the trackpitch error to adjust the track pitches of the plurality of track on themagnetic tape.

In one variation, the control circuit continues to receive trackinformation from the read-head and continuously adjust track pitches ofthe plurality of track to match corresponding magnetic transducers onthe magnetic read-head 90. This configuration allows the tape drive tocompensate for the variation in track pitch along the length of thetape. In another variation, once the track pitch on the tape is adjustedto correspond to the transducers on the read-head of the tape drive, thecontroller continues to monitor the track pitch and make necessaryadjustments to keep the track pitch on the tape constant. With the trackpitch adjusted to match the transducers on the read-head, the read-headcan then read the information stored in data tracks on the tape 92.Examples of method and apparatus for tracking lateral tape position anddetecting the position of the tracks on the tape are disclosed in U.S.patent application Ser. No. 11/084,412 entitled AUTO-SERVO TAPE SYSTEMAND ASSOCIATED RECORDING HEAD, by George A. SALIBA, file on Mar. 18,2005, which is incorporated herein by reference for all purposes.

As one of ordinary skill in the art having the benefit of thisdisclosure would appreciate, the method disclosed herein can beimplemented to stretch the tape in a localized region independent of thechanges in the overall width of the tape. However, in one variation,mechanisms that are well known to one of ordinary skill in the art canbe utilized to maintain a constant tape width, while an actuator issimultaneously utilized to adjust the stretching of the tape in alocalized region on the surface of the tape to control the track pitchof the written track in this localized region.

Referring to FIG. 9, another example of read-head/actuator combination96 is illustrated. In this variation, the magnetic read-head 4 ispositioned over the top side 98 of the tape 8 while the actuator 26 ispositioned to apply pressure to the underside of the tape 8. In onevariation, the actuator contacts the tape in a localized region with alateral dimension less than the width of the tape 8. In anothervariation, the actuator applies pressure across the width of the tape.As discussed above, a feedback loop may be established through a controlcircuit (not shown) connected to both the read-head and the actuator formodulating the track pitch of the written tracks on the tape.

FIG. 10 illustrates yet another example, where two actuators 26, 27 arepositioned on each side of the magnetic read-head 4 to apply pressure tothe surface of the magnetic tape 8. In FIG. 11, another variation, wherea single displacement mechanism 102 is configured to apply pressure tothe tape at a location immediately in front of, and immediately behind,the magnetic read-head 4. In this particular example, the contactingelements 104, 106, which are coupled to the displacement mechanism 102,are configured to extend beyond the width of the tape. In anotherexample, the contacting area is limited to a region less than the widthof the tape 8. As shown in FIG. 11, a controller 32 is coupled to theread-head and the displacement element to form a feedback loop, suchthat the controller 32 is able to monitor the track pitch and modify thepressure applied by the displacement mechanism 102 to adjust the trackpitches on the tape 8.

In another example, the read-head 4 itself is displaced into the surface28 of the tape 8 directly, as shown in FIG. 12. This displacement causeslocal stretching/expansion of the tape 8, which leads to changes intrack pitch. In one configuration, the magnetic read-head 4 is couple toan actuator that drives the magnetic read-head into and away from thetape surface. A controller (not shown) receives information regardingthe position and/or track pitch of the track on the tape from themagnetic read-head 4, and determines the amount of displacement neededon the magnetic read-head 4 to generate the desired track pitch changeson the tape. In one variation, the magnetic read-head has a lateraldimension less than the width of the tape (as shown in FIG. 12). Inanother variation, the width of lateral dimension of the read-headstructure is wider than the width of the tape.

FIG. 13 illustrates another variation where the moveable magneticread-head 4 is implemented along with two fixed-position countersupports 112, 114 placed on the other side of the tape. In the variationshown, both the magnetic read-head 4 and the two counter supports 112,114 are configured to with lateral dimension less than the width of thetape. In one variation, the read-head structure has a lateral dimensionthat is wider than the width of the tape. FIG. 14 illustrates avariation, where both the magnetic read-head 4 and its correspondingcounter supports 116, 118 are movable. For example, each of the twocounter supports 116, 118 may include an actuator (e.g., displacementmechanism, step motor, etc.). FIG. 15 shows another variation where twoactuators 120, 122 are provided next to the read-head 4 on the same sideof the tape 8. In yet another variation, two pressure delivery elements124, 126 are coupled to the magnetic read-head 4, as shown in FIG. 16.The two elements 124, 126 are positioned in front of and behind themagnetic read-head along the length of the tape 8. An actuatingmechanism (e.g., displacement mechanism, step motor, etc.) is coupled tothe read-head 4 and the two elements 124, 126 to displace themsimultaneously in a direction perpendicular to the surface of the tape8.

As one of ordinary skill in the art having the benefit of thisdisclosure would appreciate, two or more actuators may be implemented toprovide localized pressure on the surface of the tape. FIG. 17illustrated one example where two actuators 128, 130 are positioned nextto one another to deliver pressure onto the tape on one side of themagnetic read-head 4.

In another example, varying amounts of pressure are delivered onto alocalized area on the surface of the tape to induce variation amounts ofchanges in track pitch in the effected area. This design allows the userto expand the track pitch between a selective track in a give channelmore than the other tracks in the same channel. For example, as shown inFIG. 18, a single actuator 132 may have multiple elements 134 todelivering varying amounts of pressure across a section of the tape 8.In one variation, multiple actuators are aligned side-by-side andcontrolled independently by a controller to induce the desired amountchanges cross the effected area on the tape. In another variation, abuffering mechanism 136 is positioned at the distal end of the actuatingelements 138 to provide a smooth distribution of force/pressure profileacross the effected region on the tape 8, as shown in FIG. 19.

FIG. 20 illustrates yet another variation of an actuator 140 fordelivering varying amounts of force/pressure within a section along withwidth of the tape 8. A cross-sectional view of a tape 8 is shown with anactuator 140 positioned over one surface of the tape. An interfaceelement 142 is coupled to the distal end of the actuator. The interfaceelement 142 is able to pivot relative to the main rod 144 of theactuator 140. By controlling the amount of pivot on the interfaceelement 142, the controller is able to apply more pressure to one sideof the contacting region than the other.

FIG. 21 illustrates another example of an apparatus for controllingtrack pitch locally on a tape being read by a tape drive. In thisexample, the overall tape tension is held constant, and thereby,eliminating various adverse effects, such as excessive lateral tapemotion and tape damages that can result due to excessive stretching. Theapparatus utilizes the flexible properties of tape media to modify thewritten track pitch to support multi-channel high track densityrecording. The position of the tracks 152 relative to the magneticread-head 154, which may include both write and read cores, is extractedfrom the signal collected by read-head. The apparatus 156 controls theoperating point of the pitch controls system in a manner that provide acore pitch match between the cores across the read-head 154 and thewritten tracks 152 on the tape (i.e., matching the transducers 158 onthe read-head 154 to the written tracks 152 on the tape 160). In onevariation, the system utilizes adaptive learning to control the trackpitch on the tape. This configuration may allow a multi-channel drive tooperate at higher track densities and across a wider range of humidityand temperatures.

As illustrated in FIG. 21, a series of magnetic transducers 158 arepositioned on the magnetic read-head 154 to detect changes in magneticflux in the plurality of written tracks 152 on the magnetic tape 160.The actuator 164 comprises a roller configured to apply pressure to alocalized region of the tape 160. In this example, the roller 164applies pressure onto a localized region with a width of W₃, where W₃ isless than the width of tape W₄. The roller 164 is configured such thatby rotating the roller along its axis, the system can vary the amountthe roller 164 is displaced towards or retracted from the surface of thetape 160. In one variation, as the roller is rotated in the counterclockwise direction 166, the roller displaces a contacting interface 168towards the tape surface, resulting in an increase in the depressioninduced by the roller 164. As the roller 164 is rotated in the clockwisedirection, the roller displaces the contacting interface away from thetape surface, resulting in a decrease in the depression induced by theroller.

In one variation, the roller comprises a rollable drum 170, FIG. 22. Therollable drum 170 has a cross-section area of a compressed circle (e.g.,oval, etc.). A step motor 172 (or other displacement mechanism) iscoupled to the axis of the rollable drum 170 to control theposition/rotation of the drum 170. By rotating the drum 170 in thecounter clockwise direction 174, thus forcing the elongated section ofthe drum into the surface 178 of the tape 180, one can induce stretchingof the tape in a localized region in and surrounding the area when thedrum 170 contacts the tape. By modulating the position of the drum 170,the apparatus can control the track pitch of the written tracks 182 inthe localized region.

In another design, a tape drive is configured to utilize pre-writtenservo track as reference to adjust the lateral position of the tapeand/or the overall tension of the tape, while at the same timeimplements track pitch control function to modulate track pitch in alocalized region on the tape. For example, the pre-written servo trackmay be written in a controlled environment with controlled tension. Thetape drive can then adjust the tape's lateral position and/or overalltension during initial write as well as subsequent reads, minimizing therequired tension spread for compensation. An actuator is utilizedsimultaneously to fine tune the track pitch to ensure that the datatracks on the tape matches the corresponding magnetic transducers on theread-head.

In another variation, a read-head with a contour for facilitating and/orinducing read-head to tape contact, when the tape is passed under theread-head at high speed, is implemented on the tape drive along with thepitch control function. For example, a read-head having a plurality ofactive data islands and a desirable wrap angle, as shown in FIG. 23, canbe implemented in the tape drive. The exemplary magnetic read-head 220includes active data islands 224 having mini-outriggers (not shown). Themagnetic read-head 220 comprises both read and write transducers,wherein a given section of the tape is first written upon by writetransducers, and thereafter checked by read transducers. A tape 230 isdrawn over the support surface 222 and the surfaces of islands 224,which include active device regions (not shown) having a plurality oftransducers, e.g., read or write transducers. Additionally, tape 230 isdrawn over primary outriggers 226. Active device regions may include,for example, a column of 16 write transducers and a column of 16 readtransducers.

Further, an arrow shown on tape 230 indicates the reversible directionof tape 230 movements relative to magnetic read-head 220, and an arrowshown on read-head 220 indicates the relative movement of the read-head220 to the path of tape 230 in a direction generally orthogonal (i.e.,lateral movement) to the direction of tape 230 advancement. The movementof magnetic tape read-head 220 allows head 220 to align read and/orwrite transducers in the active regions to read and/or write informationalong one or more different data tracks arranged longitudinally alongtape 230; for example, a suitable servo system may send position signalsto a controller which in turn controls an actuator for translatingread-head 220 in a lateral movement relative to tape 230. A secondactuator (not shown), can be positioned next to the read-head 220 forapplying a pressure onto a localized region of the tape 230 (in adirection perpendicular to the tape surface) to induce changes in thetrack pitches in an active regions to be read and/or write by thetransducers in the read-head.

In another variation, a negative pressure flat head contour design isimplemented in the apparatus. In yet another variation, the read-headcontour is selected such that it can handle significant tension changein the tape while maintaining contact with the tape surface to read thedata from the tape. As one of ordinary skill in the art having thebenefit of this disclosure would appreciate, specific head contours maybe implemented to permit the read-head to operate over the rage ofresultant local tape surface tension changes.

Variations of the apparatus may be configured to correct variousoff-track pitch errors between the tape and the read-head, such as,errors resulting from interchanging between heads (e.g., mismatchbetween write-head and read-head), servo writer head core pitch error,and/or initial tape width variance (when the tape servo tracks werewritten), by temporarily changing track pitch on the written tracks tomatch the read-head. Moreover, variations of the apparatus may minimizetape edge damage and/or decrease problems associated with spooling atvariable tension.

This invention has been described and specific examples of the inventionhave been portrayed. While the invention has been described in terms ofparticular variations and illustrative figures, those of ordinary skillin the art will recognize that the invention is not limited to thevariations or figures described. In addition, where methods and stepsdescribed above indicate certain events occurring in certain order,those of ordinary skill in the art will recognize that the ordering ofcertain steps may be modified and that such modifications are inaccordance with the variations of the invention. Additionally, certainof the steps may be performed concurrently in a parallel process whenpossible, as well as performed sequentially as described above.Therefore, to the extent there are variations of the invention, whichare within the spirit of the disclosure or equivalent to the inventionsfound in the claims, it is the intent that this patent will cover thosevariations as well. Finally, all publications and patent applicationscited in this specification are herein incorporated by reference intheir entirety as if each individual publication or patent applicationwere specifically and individually put forth herein.

1. A tape drive comprising: a read-head having a plurality oftransducers operable to read data from a plurality of tracks on a datastorage tape; and an actuator operable to adjust at least one trackpitch of the tracks on the data storage tape by directly engaging a tapesurface of the data storage tape to improve alignment between the trackson the data storage tape with the transducers.
 2. The tape driveaccording to claim 1, wherein the actuator is operable to expand orcontract a localized region on the data storage tape to match each ofthe tracks in the localized region with a corresponding transducer onthe read-head.
 3. The tape drive according to claim 1, wherein theactuator is operable to modulate a tape tension in a localized area onthe data storage tape to adjust the track pitches of the tracks in thelocalized area, and the localized area has a lateral dimension less thanthe width of the tape.
 4. The tape drive according to claim 2, where theactuator is operable to expand or contract a localized region on thedata storage tape by applying varying amounts of pressure onto the tapesurface.
 5. The tape drive according to claim 4, wherein the pressureapplied onto the tape surface is applied on an area with a lateraldimension that is less than 50% the width of the data storage tape. 6.The tape drive according to claim 1, further comprising: a controllerconnected to the read head and the actuator.
 7. The tape drive accordingto claim 6, wherein the controller is operable to monitor the positionof the tracks and control the actuator to adjust track pitches of thetracks on the data storage tape.
 8. The tape drive according to claim 6,wherein the controller comprises a feedback circuit for monitoringpositions of the tracks on the data storage tape and adjusting apressure applied by the actuator onto a surface on the data storage tapeto maintain alignment between the tracks on the tape and the transducerson the read-head.
 9. A method of operating a magnetic tape drive whichtransduces data to and from a magnetic tape, the method comprising:reading data on the magnetic tape with a magnetic read-head, wherein themagnetic read-head comprises a plurality of transducers forsimultaneously reading data from a plurality of tracks on the magnetictape; and adjusting at least one track pitch of the plurality of trackson the magnetic tape by touching a tape surface of the magnetic tape toimprove alignment between the tracks on the magnetic tape andtransducers on the magnetic read-head.
 10. The method according to claim9, wherein adjusting the track pitch comprises expanding or contractingthe tape in order to match each of the tracks to a correspondingtransducer on the magnetic read-head.
 11. The method according to claim9, wherein adjusting the track pitch comprises modulating a tape tensionin a localized area on the tape.
 12. The method according to claim 11,the localized area having a lateral dimension less than the width of thetape.
 13. The method according to claim 10, wherein expanding orcontracting the tape comprises decreasing or increasing a pressureapplied on the tape surface of the tape.
 14. The method according toclaim 13, wherein the pressure applied on the surface of the tape isapplied on a localized region relative to a width of the tape.
 15. Themethod according to claim 14, wherein the pressure applied on thesurface of the tape is applied on an area with a lateral dimension thatis less than 50% the width of the tape.
 16. The method according toclaim 9, wherein adjusting the track pitch comprises varying the trackpitches of the plurality of tracks to identify a match between thetracks and the transducers.
 17. The method according to claim 10,wherein adjusting the track pitch comprises minimizing a mismatch inlateral positions between the tracks and the magnetic transducers. 18.The method according to claim 9, wherein adjusting the track pitchcomprises varying a pressure on a localized region on the tape to inducea change in the track pitches.
 19. The method according to claim 18,wherein the localized region is less than the width of the tape.
 20. Themethod according to claim 18, wherein the pressure is applied with anactuator.
 21. The method according to claim 18, wherein the pressure isapplied by moving the magnetic read-head into a surface of the magnetictape.
 22. The method according to claim 9, wherein adjusting the trackpitch comprises varying a position of the magnetic read-head.
 23. Themethod according to claim 13, wherein the pressure is applied to an areahaving a lateral dimension less than a width of the tape.
 24. The methodaccording to claim 9, wherein adjusting comprises stretching a firstarea on the tape while keeping tension in a second area surrounding thefirst area at a constant level.
 25. The method according to claim 9,further comprising: monitoring positions of at least two data tracks onthe magnetic tape.
 26. The method according to claim 9, furthercomprising: monitoring positions of at least two of the plurality oftracks on the magnetic tape, wherein the at least two of the pluralityof tracks on the magnetic tape comprise data tracks; detecting a servotrack on the magnetic tape; and adjusting a lateral displacement of themagnetic tape based on the servo track.
 27. A method of reading datafrom a magnetic tape, the method comprising: detecting track pitches ofa plurality of tracks on a magnetic tape; and continuously adjusting atleast one track pitch of the plurality of tracks by physicallycontacting a surface of the magnetic tape to match correspondingmagnetic transducers on a magnetic read-head.
 28. The method accordingto claim 27, wherein at least two of the plurality of tracks on themagnetic tape comprise data tracks, and at least one of the plurality oftracks on the magnetic tape comprises a servo track.
 29. The methodaccording to claim 27, further comprising: reading data from at leasttwo of the plurality of tracks.
 30. The method according to claim 27,further comprising: positioning the tape laterally based on the servotrack.
 31. The method according to claim 30, wherein continuouslyadjusting track pitches comprises applying a pressure to a localizedarea on the magnetic tape.
 32. The method according to claim 27, furthercomprising: detecting a servo track; and laterally adjusting a positionof the magnetic tape relative to the magnetic read-head.
 33. The methodaccording to claim 32, wherein continuously adjusting the track pitchcomprises applying a pressure on a localized area on a face of themagnetic tape.
 34. The method according to claim 33, wherein thelocalized area has a lateral dimension and the tape has a width morethan twice the lateral dimension of the localized area.
 35. The methodaccording to claim 32, wherein continuously adjusting the track pitchcomprises applying varying amounts of pressure on an area on a topsurface of the tape, wherein the top surface comes into contact with themagnetic read-head.
 36. The method according to claim 35, wherein thearea has a lateral dimension less than the width of the magnetic tape,and continuously adjusting the track pitch further comprises utilizing apredetermined algorithm to locate a best match between the plurality oftracks and the corresponding magnetic transducers on the magneticread-head.
 37. The method according to claim 27, wherein continuouslyadjusting the track pitch comprises applying varying amounts of pressureon an area at a top surface of the tape, wherein the top surface comesinto contact with the magnetic read-head, and the area has a lateraldimension less than the width of the magnetic tape.
 38. The methodaccording to claim 27, wherein the plurality of tracks comprises atleast two outer tracks on a channel being read by the read-head.
 39. Themethod according to claim 38, further comprising: detecting a servotrack; and laterally adjusting a position of the magnetic tape relativeto the magnetic read-head.
 40. The method according to claim 27, whereincontinuously adjusting the track pitch comprises varying a position ofthe magnetic read-head to increase or decrease a pressure between themagnetic read-head and the tape.
 41. The method according to claim 27,wherein continuously adjusting the track pitch comprises applyingvarying amounts of pressure on each of the plurality of tracks to adjustthe track pitch.
 42. The method according to claim 27, whereincontinuously adjusting the track pitch comprises applying pressures on aplurality of areas on the tape.